This protocol investigates unanswered questions regarding the immune response to the Oka/Merck strain of Varicella vaccine. This vaccine, named VARIVAX, has recently been licensed by the FDA for administration to healthy non-VZV-immune individuals. In this study VARIVAX is offered to non-VZV-immune children as a single subcutaneous dose and to non-VZV-immune adolescents and adults as two subcutaneous injections, administered 4-8 weeks apart. This schedule is in accordance with the recommendations provided in the vaccine package insert. Blood is obtained before and after vaccination to investigate the immune response to this vaccine.